The present invention relates to a rotary multi-position magnetic detent device.
There are control mechanisms with transducers which generate electrical signals and which have mechanical detents. For example, vehicle operator controls commonly use detents to provide the operator with tactile feedback in response to manipulation of the control mechanism. It is desirable for the electrical signals produced by the mechanism to be coordinated with its mechanical feel. However, since mechanical detents are subject to friction and mechanical wear, it is difficult to provide such coordination over the entire life of such a mechanism, without requiring some type of calibration or adjustment at initial assembly and perhaps periodically thereafter.
U.S. Pat. No. 3,934,216 describes a rotary multi-position detent device with a plurality of detent positions defined by magnetic fields established by a rotor and stator with magnets sandwiched therebetween. The magnetic poles of the magnets are oriented axially and the variation in magnetic field is created by radially projecting inner and outer pole pieces. Thus, the radially projecting pole pieces increase the radial dimensions of the device, and the detent effect is limited since it is produced solely by variations in attractive magnetic forces.
Accordingly, an object of this invention is to provide a compact rotary multiposition magnetic detent device.
A further object of the invention is to provide such a detent device with strong magnetic detents.
These and other objects are achieved by the present invention, wherein a rotary detent device includes an inner member having an outer cylindrical surface and an outer member receiving the inner member. The outer member has an inner cylindrical surface and the outer member rotates relative to the inner member.
Inner magnets are disposed in the outer surface and distributed regularly and peripherally around the outer surface. The inner magnets have radially oriented magnetic poles, and alternate adjacent ones of said inner magnets have alternate radially outwardly directed north and south poles. Outer magnets are disposed in the inner surface and distributed regularly and peripherally around the inner surface. The outer magnets have radially oriented magnetic poles, and alternate adjacent ones of the outer magnets have alternate radially inwardly directed north and south poles. As the inner and outer members are rotated with respect to each other, the inner and outer magnets generate opposing and attracting forces each other to form a plurality of magnetic detent positions. A magnetic field sensor generates a signal in response to relative rotation of the inner and outer members.